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CTBUH Research Report
Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa, and Donald Davies
Life Cycle Assessmentof Tall Building Structural Systems
Bibliographic Reference:Trabucco, D., Wood, A., Popa, N., Vassart, O. & Davies, D. (2015) Life Cycle Assessment of Tall Building Structural Systems. Council on Tall Buildings and Urban Habitat: Chicago.
Principal Research Investigators: Dario Trabucco, Antony Wood, Olivier Vassart, Nicoleta Popa & Donald DaviesAdditional Researchers: Meysam Tabibzadeh, Eleonora Lucchese, Mattia Mercanzin & Payam BahramiEditorial Support: Jason GabelLayout: Mattia Mercanzin & Marty Carver
Published by the Council on Tall Buildings and Urban Habitat (CTBUH) in conjunction with ArcelorMittal
© 2015 Council on Tall Buildings and Urban Habitat
Printed and bound in the USA by The Mail House
The right of the Council on Tall Buildings and Urban Habitat to be identifi ed as author of this work has been asserted by them in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.
All rights reserved. Apart from any fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any means, electronic, mechanical, photocopying, recording or otherwise, without the written permission of the publisher.
Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identifi cation and explanation without intent to infringe.
Library of Congress Cataloging-in-Publication DataA catalog record has been requested for this book
ISBN: 978-0-939493-48-7
Council on Tall Buildings and Urban Habitat
S.R. Crown Hall
Illinois Institute of Technology
3360 South State Street
Chicago, IL 60616
Phone: +1 (312) 567-3487 Fax: +1 (312) 567-3820
Email: info@ctbuh.org
www.ctbuh.org
www.skyscrapercenter.com
CTBUH Asia Headquarters Offi ce
College of Architecture and Urban Planning, Tongji University
1239 Si Ping Rd, Yangpu District, Shanghai, China 200092
Phone: +86 21 65982972
Email: china@ctbuh.org
CTBUH Research Offi ce
Iuav University of Venice
Dorsoduro 2006, 30123 Venice, Italy
Phone: +39 041 257 1276
Email: research@ctbuh.org
Front Cover: Image sources; Clockwise from top left: FreeImages.com/Bo de Visser; Marshall Gerometta, (cc-by-2.0) U.S. Army Materiel Command, mzacha via RGBStock, FreeImages.com/steph poitiers
Research Funded By:
Principal Researchers / Authors
Dario Trabucco, Research Manager, CTBUH / Iuav University of Venice
Antony Wood, Executive Director, CTBUH / Illinois Institute of Technology / Tongji University
Olivier Vassart, Head of Global R&D Long Carbon, ArcelorMittal
Nicoleta Popa, Senior Research Engineer, ArcelorMittal
Donald Davies, Principal, Magnusson Klemencic Associates
Additional Researchers / Contributors
Eleonora Lucchese, CTBUH Research Offi ce, Venice
Mattia Mercanzin, CTBUH Research Offi ce, Venice
Meysam Tabibzadeh, CTBUH Research Offi ce, Chicago
Payam Bahrami, CTBUH Research Offi ce, Chicago
Contributors / Project Steering / Peer Review Panel
Mark Aho, McNamara / Salvia
Peyman Askarinejad, Arabtec
Martina Belmonte, CTBUH/IUAV
Joseph Burns, Thornton Tomasetti
Luis Simoes Da Silva, University of Coimbra
Edward DePaola, Severud Associates
Chukwuma Ekwueme, Weidlinger Associates
Paul Endres, Endres Studio
David Farnsworth, Arup
Rolf Frischknecht, Treeze
Erleen Hatfi eld, Buro Happold
Ben Johnson, Skidmore, Owings & Merrill
Leif Johnson, Magnusson Klemencic Associates
Makoto Kayashim, Taisei
Raff aele Landolofo, University of Naples
Dennis McGarel, Brandenburg
Declam Morgan, Buro Happold
Levon Nishkian, Nishkian Menninger
Tatsuo Oka, Utsunomiya University
Arif Ozkan, Arup
Stefano Panseri, Despe
John Peronto, Thornton Tomasetti
Dennis Poon, Thornton Tomasetti
Christopher Rockey, Rockey Structures
Ronald Rovers, RiBuilIT
Tim Santi, Walter P Moore
Allen Thompson, WSP
Robert Victor, Brandenburg
John Viise, Thornton Tomasetti
Wolfgang Werner, Urban Fabrick
Yong Wook Jo, Arup
Nabih Youssef, Nabih Youssef & Associates
4
5
Contents
About the CTBUH 6 About ArcelorMittal 6 About the Authors 7
Preface 8
1.0 Tall Buildings Today 12
1.1 Role of Structural Systems in a Tall Building 14 1.2 Review of Current Structural Systems in Tall Buildings 16 1.3 Foundation Types 21
2.0 Sustainability and Tall Buildings 24
2.1 Energy Consumption of Tall Buildings 27 2.2 Embodied Energy of Tall Buildings 30
3.0 Life Cycle Assessment 32 3.1 Explanation of ISO LCA 34 3.2 Defi nition of the Goal of the Study 35 3.3 Scope Defi nition of this Study 36 3.4 Scenario Analysis and Identifi cation of 37 Functional Units 3.5 System Boundaries 40 3.6 Structural Systems and Materials 40 3.7 Floor Systems Used 40 3.8 Inventory of Materials 41
4.0 Steel: Cradle to Grave 44
4.1 Steel Production 46 4.2 Structural Steel Profi les 48 4.3 Steel Plates 48 4.4 Steel Fabrication 49 4.5 Steel Rebar 50 4.6 Welded Wire Fabric 51 4.7 Metal Decking 52 4.8 Steel Production Inventory Data 53 4.9 Life Phase 54 4.10 Recycling 55
5.0 Concrete: Cradle to Grave 58 5.1 Cement Production and Transportation 60 5.2 Cement Substitutes 61 5.3 Gravel, Sand, and Aggregates 64 5.4 Concrete Production and Transportation 65 5.5 Environmental Data for Concrete 66 5.6 Recycling of Concrete and Aggregates 68
6.0 Fireproofi ng Materials: Cradle to Grave 70
6.1 Types of Fireproofi ng Materials 73 6.2 Environmental Impacts of Fireproofi ng Materials 74
7.0 Transportation and On-Site Energy Use 76
7.1 Transportation and On-Site Operations in Literature 78 7.2 Transportation 81 7.3 Crane Operations 81 7.4 Concrete Pumping 83 7.5 Formworks 84 7.6 Foundations 84
8.0 The End-of-Life of Tall Buildings 86
8.1 High-Rise Demolition Techniques 88 8.2 Impact of Structural Materials on the 90 End-of-Life of Tall Buildings 8.3 Energy Use in Demolition 91 8.4 Transportation Assumptions for Debris 93 8.5 Sources of Data on Tall Building Demolition 94
9.0 Inventory of Materials and Research Results 96
9.1 The Assessment of Two Environmental Impacts 98 9.2 Comments on the Selected Indicators 98 9.3 Research Results 99 9.4 Comparison with Literature Results 99 9.5 General Research Conclusions 102 9.6 Future Research 107
10.0 Appendix: Detailed Results of Each Modelled Scenario 112
Acknowledgements 178
Bibliography 179
8
Preface
Despite the history of the skyscraper
spanning well over a century, and the
fact that the world is now constructing
tall buildings in excess of 1,000 meters in
height, with the exception of the events of
9/11, we have never actually demolished
or dismantled a building taller than 187
meters. That building was the Singer
Building, a 187-meter tower in New York
City that was demolished in 1968 to make
way for 1 Liberty Plaza. The reality is that
we are now building many hundreds of
skyscrapers – in addition to those already
in existence – with little idea about
their real longevity, what variances and
experiences they will have during their
whole life cycle, and what will happen to
them at the end of that life cycle.
These are massively important issues
that should infl uence the design of all
skyscrapers from the very outset (i.e.,
how to design buildings for multiple
changes in function, an indeterminate
future, or even perpetual existence?),
but the industry does not even have
a template for assessing the relative
implications – energy or otherwise – of the
diff erent stages of a building’s life. In the
sustainability realm, emphasis has been
placed on the reduction of operational
energy at the expense of all other facets.
While the reduction of operating energy
is vitally important, it is far from the
complete picture. Reducing the embodied
energy of the materials in the building
itself is equally important. As technologies
increasingly allow buildings to move
towards carbon-neutral operation (though
we are still far away from that holy grail),
embodied energy will become the main
energy consumer, and thus it is the most
critical area for further consideration now.
In short, the true environmental impact
of the full life cycle of tall buildings is a
signifi cantly unknown quantity.
This is the point of departure for this
guide, and the three-year research project
that underpins it. A Life Cycle Assessment
(LCA) is a methodology that gauges
the consequences of human actions by
analyzing the fl ow of materials used in
a product or a building and traces the
environmental impacts linked to each
stage of its life cycle. An LCA thus begins
by analyzing the eff ects of material
extraction and processing, accounting
for the specifi c pieces of equipment
used and the energy needed to turn
raw materials into a fi nal product (in this
case, a building). The assessment also
evaluates the impacts of manufacturing,
transportation, and on-site construction
activities, taking note of both power
consumption and carbon emissions
during each process. Finally, operational
activities, demolition, and end-of-
life recycling are considered. When
information from each stage is combined,
a holistic picture of environmental
impacts can be formed for a given
product, one that acknowledges the
various actions that are required to bring
a single entity into existence through
contemporary means.
The true benefi ts of the LCA methodology
are realized when numerous assessments
are performed for diff erent versions of
a product. This allows researchers to
compare alternatives along various impact
categories, and provides a basis for making
informed decisions that produce the
greatest environmental benefi ts over time.
Given this fact, it is clear that Life Cycle
Assessment is largely the missing piece in
the sustainable puzzle for tall buildings.
This research, which was undertaken
by the CTBUH Research Division and
sponsored by multinational steel
manufacturer ArcelorMittal, identifi es and
compares the life cycle implications for
multiple comparative structural systems
found in 60- and 120-story buildings.
Structural systems are by no means the
entirety of a tall building, and an LCA of
the components that are more likely to
change over time (façades, MEP systems,
interior fi t out) would also be extremely
valuable. However, the means to evaluate
life cycle energy is still in its infancy and
is an especially complicated subject.
Thus, for this fi rst study, focusing on the
structural systems of a building – which
accounts for a large share of the material
inventory and has major impacts on all
aspects of building performance – seemed
a sensible choice.
This report thus represents the fi rst-ever
full LCA on tall building structural systems
ever performed, and represents a “fi rst
stab” at environmentally quantifying
the decisions made in the design and
engineering process of skyscrapers.
Using the results found herein, industry
professionals and researchers can
recognize the performance of these
systems along two key impact categories:
Global Warming Potential (GWP) and
Embodied Energy (EE). Global Warming
Potential is measured by calculating the
amount of carbon (or carbon equivalent)
that is released over the course of a
structure’s life cycle, allowing impacts
on climate change to be determined.
Embodied Energy was selected as an
indicator for natural resource depletion,
since the amount of energy consumed
over the lifetime of the structural systems
and their materials has direct implications
9
for the consumption of electricity, fossil
fuels, and natural gas.
In addition to this report’s ability to serve
as a reference in the design process, it also
serves as a launching point for further
research into the life cycle of tall buildings.
Indeed, as is typical with undertakings of
this nature, more questions tend to arise
than answers. From the outset, it was the
Council’s goal to explore this topic with
an emphasis on fi nding where further
investigation is needed. Suggestions
for further research are thus provided at
length in the fi nal section of the report.
As evidenced in this study, the CTBUH
Research Division plays a very important
role, not only in achieving the Council’s
mission of disseminating information
on tall buildings to professionals and
stakeholders around the world, but
to engage in the global debate on
sustainability that has relevance far
beyond the industry itself. The CTBUH is
well-positioned for research such as this
due to its intermediary role between a
diverse set of professionals, with members
and contributors ranging from architects,
engineers, material specialists, owner/
developers, city planners, construction
companies, and equipment suppliers.
The Research Division is one of the ways
that the Council uses these resources to
address the research gaps identifi ed in the
Roadmap on the Future Research Needs of
Tall Buildings, a 2014 CTBUH publication
that lists and prioritizes topics that are
in greatest need of further exploration.
By focusing the eff orts of the CTBUH in
this way, attention is brought to often
ignored or underrepresented aspects of
tall buildings, mobilizing individuals to
obtain a more complete understanding of
the industry.
The daunting complexities of life cycle
research require the collaboration
between numerous individuals within
varying specializations. This LCA alone
drew on the support and expertise of
numerous companies, all of whom are
acknowledged on page 178. Thus, this
project is truly an indication of concern
for many in the tall building industry
regarding the “big picture” of sustainability
for our cities. So let this report serve
not only as a plunge into an emerging
fi eld of study, but a call to action that
emphasizes the importance of looking at
the consequences of our choices, from
beginning to end.
Antony WoodChicago, USA
Dario TrabuccoVenice, Italy
Figure 1.2: Equitable Life Building, 1870, New York, considered by some to be the fi rst tall building in
history due to its exploration of the potentialities off ered by the passenger elevator
Source: (public domain) Emerson7
Figure 1.1: Home Insurance Building, 1885, Chicago,
generally accepted as the fi rst tall building because of its
curtain wall construction on a steel frame.
12
The Council on Tall Buildings and Urban
Habitat (CTBUH) recognizes three diff erent
ways of defi ning a tall building. According
to the CTBUH, tall buildings exhibit some
element of “tallness” in one or more of the
following categories:
• Height Relative to Context: a building
is taller than those in the surrounding
area with respect to a prevailing
urban norm;
• Proportion: a tall building has a
slender appearance made evident by
a relatively small base in comparison
to its height;
• Tall Building Technologies: a building
contains technologies which may be
attributed as being a product of its
height (e.g. specifi c vertical transport
technologies, structural wind bracing
as a product of height, etc.).
In addition to the above criteria, there are
two defi nitions that establish universal
height thresholds for tall buildings: the
CTBUH defi nes “supertall” buildings as
those over 300 meters in height, and
“megatall” buildings as those over 600
meters in height. Although great vertical
strides are currently being achieved by
an increasing number of tall buildings
every year, there are only 93 supertall and
three megatall buildings completed and
occupied globally as of June 2015.
The birthplace of the tall building
typology is still a heavily debated topic
among experts. However, it is commonly
agreed that the fi rst tall buildings in
history were found in New York and
Chicago (Barr, 2014).
An early observation by Fryer (Fryer,
1891) mentions three basic elements that
contributed to the birth of skyscrapers:
1.0 Tall Buildings Today
| Tall Buildings Today
Figure 1.3: Load bearing wall system for skyscrapers
Monadnock Building, Chicago, (Floor Plan)
Source: Leslie, Thomas (2013), “The Monadnock Building, Technically Revisited” CTBUH Research Paper, 2013 Issue IV,
pp 29. Redrawn by CTBUH
13
the modern passenger elevator, the
invention of iron/steel structures (see
Figure 1.1), and the terracotta fl at arch
element to protect horizontal iron beams
from fi re. Rem Koolhaas (Koolhaas, 1978),
almost one century later, also cites steel
frameworks and the passenger elevator as
the elements that made the construction
of tall buildings possible.
Both of the above defi nitions exclude
several notable examples of buildings
that, despite having a load bearing
masonry wall system (such as the 1893,
17-story Monadnock Building in Chicago),
can clearly be considered a tall building
(Leslie, 2013).
Considering this argument, the elevator
is the only remaining determinant for a
tall building. In this case, the Equitable
Life Building (see Figure 1.2), completed
in New York in 1870, would be the fi rst
tall building in the history due to its
exploration of the potentialities off ered by
the passenger elevator (Weisman, 1970).
The increased heights and diff erent shapes
that New York skyscrapers adopted as
a result of the 1916 Zoning Resolution,
which also aff ected the design of tall
buildings in all other American cities
(Willis, 1986), did not alter the basic
structural schemes used since the birth
of the skyscraper typology. In fact, from a
structural perspective, all skyscrapers built
before the Second World War are quite
similar, and were based on the principle
of a rigid frame, with required stability
against lateral loads provided by the
stiff ness of beam-column connections
(Ali & Moon, 2010) as well as the natural
bracing eff ect provided by the solid façade
panels. The solid decorated urban blocks
used in early skyscrapers evolved since the
1950’s toward a more neat and transparent
style that spread all over the world in a
movement known as the “International
Style.” Even if virtually all tall buildings have
a façade freed from any load bearing or
structural function, the International Style
marked an evolution in the performance
of tall buildings. Fully glazed and sealed
façades, introduced for the fi rst time in
buildings such as the Lever House in New
York and the Commonwealth Building in
Portland, Oregon, dramatically reduced
the thermal inertia of buildings.
This lead to an increase in the reliance
on mechanical air conditioning and
ventilation systems, together with the
thermal inertia of the internal structure
and surfaces. Glazed façades also
signifi cantly reduced the weight of tall
buildings, while also taking away the solid
walls punctuated by small windows that
provided bracing against lateral loads.
As a consequence of this, and of the
increasing height and slenderness of tall
buildings, bracing functions were later
transferred toward the interior by creating
braced trusses around the elevator core.
Thus, using these new features, the
modern tall building typology was born.
One of the earliest examples of these
features can be found in the Seagram
Building in New York.
Since the end of the Second World War, tall
buildings have spread from their country
of origin, the United States of America, to
become a global symbol of modernity and
Tall Buildings Today |
Figure 2.1: Integrated wind turbine example:
Bahrain World Trade Center, 2008, Manama
Source: (cc-by-sa) Ayleen Gaspar
26
Skyscrapers are often accused of being
a non-sustainable building typology
because they require a greater amount
of energy to operate compared to a
normal building, they require increased
quantities of materials for their structures
as a consequence of their height, and they
involve a higher amount of embodied
energy used to produce these materials.
Indeed, tall buildings require more
structural materials than lower buildings
and they utilize additional features (such
as elevators) that are not needed in
shorter buildings.
The environmental sustainability issues of
tall buildings became evident in 1973-
1974 when the fi rst energy crisis caused
a rise in oil and energy prices in western
countries. During the years following 1974,
extensive analyses were carried out in
North American cities to determine the
actual energy performances of tall offi ce
buildings (Stein, 1977), while technical
innovations were introduced to decrease
their overall energy consumption (mostly
in the fi eld of mechanical ventilation and
internal illumination), thus creating a
new generation of effi cient tall buildings.
Since then, tall buildings have undergone
buildings with extensive use of “visible”
sustainable principles exist today. This is
mainly due to the increased construction
and management costs associated
with developing such buildings, which
need to be addressed by drivers beyond
basic design factors. In fact, most high
performance buildings have been built
using less visible – but nonetheless
eff ective – measures, rather than bold,
outstanding innovations with very high
capital costs. Thanks to the use of modern
curtain wall systems, the exploitation
of natural ventilation, energy effi cient
major transformations that have changed
not only the energy needed for their
daily operations, but their architectural
appearance as well.
Sustainability has clearly become a
major driver of change in tall building
development, and the integration of
“green” solutions has resulted in a whole
new family of towers (Yeang, 1996)
that have inspired the introduction
of a new vernacular for tall buildings
(Wood, 2007) (Yeang, 1996). However,
green architectural features have been
used sporadically, and only a few tall
2.0 Sustainability and Tall Buildings
“Sustainability has clearly become
a major driver of change in tall building
development...”
| Sustainability and Tall Buildings
Figure 2.2: Photovoltaic façade example:
Palazzo Lombardia Building, 2011, Milan
Source: Dario Trabucco
Figure 2.3: Integrated wind turbine example:
Pearl River Tower, 2013, Guangzhou
Source: Tansri Muliani
27
elevators, combined heat and power
units, and intelligent building control
systems (Ali & Armstrong, 2008), buildings
consume far less energy than their 1970s
predecessors (Oldfi eld, et al., 2009).
With a decrease in the energy
consumption of tall buildings, a new issue
arose, requiring the renewed attention
of building experts and professionals:
life cycle thinking. In fact, buildings
consume energy and cause emissions,
not only during use, but throughout their
entire lives. From material production,
construction, and maintenance, to
demolition and the recycling of building
materials (or disposal into a landfi ll), they
consume energy as well as emit gases
and substances into the environment.
All of these phases have an impact on
the total life cycle performance of a tall
building, and one should make sure
that the benefi ts of an energy reduction
strategy (such as the use of a double
skin façade) are carefully studied, so as
not to create bigger drawbacks for other
environmental characteristics; for example,
by augmenting the initial embodied
energy that off sets the benefi ts created in
daily energy consumption.
2.1 Energy Consumption of
Tall Buildings
The energy consumption of tall buildings
evolved signifi cantly over the past 100
years, reaching a maximum before the
fi rst energy crisis and then diminishing
remarkably (Oldfi eld, et al., 2009). The
theoretical limit of 90 kWh/m2 per year
mentioned by Raman (Raman, 2001)
excludes the presence of on-site energy
generation. Thanks to the exploitation of
renewable sources such as photovoltaic
cells or wind turbines, tall buildings can
be not only effi cient in consuming energy,
but also in producing it.
Photovoltaic panels are being installed on
a number of tall building’s rooftops, such
as the Euro Tower in Rome, or façades, as
on the Palazzo Lombardia in Milan (see
Figure 2.2), but their eff ect is limited to
the surface of their external envelopes,
which are quite limited when compared to
the building’s usable fl oor area. Therefore,
their energy production rate is small
when compared to the high energy
consumption of the whole building.
Only a few tall buildings with integrated
wind turbines have been built; the Strata
Tower in London, the Bahrain World Trade
Center in Bahrain, and the Pearl River Tower
in Guangzhou (see Figure 2.3) are probably
the most relevant examples. Generally
speaking, renewable energy production
systems are not as eff ective as expected,
and cause many drawbacks to the comfort
of a tower’s inhabitants (noise, vibrations,
etc.). These drawbacks prevent their
full exploitation and require mitigation
measures (Killa & Smith, 2008) in the use of
such systems, which have to be carefully
assessed from a life cycle perspective.
Sustainability and Tall Buildings |
34
“...Life Cycle Assessment (LCA) is a methodology
aimed at assessing the environmental
consequencesof human actions,
particularly the production of goods.”
or on a process analysis. Such systems
try to take advantage of the positive
aspects of the two main methods
by combining them to perform a
quick, comprehensive, and detailed
LCA analysis. Hybrid systems are still
relatively under development but they
seem to be very promising for the
future (Zamagni, et al., 2008).
For the purposes of this study, a process-
based analysis was adopted, as described
in the International Reference Life Cycle
Data System Handbook (JRC, 2010), a
handbook released by the European
Union’s Joint Research Centre, Institute for
Environment and Sustainability, to guide
users through the steps described in more
general terms by ISO Norm 14044:2006.
3.1 Explanation of ISO LCA
ISO Norms 14040:2006 and 14044:2006
are the reference standard for the LCA.
According to ISO 14040:2006 (see Figure
3.1), a LCA is composed of four phases:
• Goal and scope defi nition: the
defi nition of a study goal indicates
whether the analysis is meant to
simply provide a data set for a
process – thus a Life Cycle Inventory
(LCI) is its main deliverable – or a
complete LCA analysis in which the
Life Cycle Inventory is interpreted
and compared to similar results for
other processes or goods. The goal
defi nition also identifi es the intended
purpose of the study (i.e., comparison
of similar products) and the target
audience. In the scope defi nition, the
subject of the analysis is identifi ed
and described in line with what was
stated in the goal defi nition. This
includes the identifi cation of the
system boundaries and the functional
unit; the analysis on the consistency
of the methods; assumptions and
Developed during the 1990’s, Life Cycle
Assessment (LCA) is a methodology
aimed at assessing the environmental
consequences of human actions,
particularly the production of goods. In
the past two decades, LCA analysis has
become more and more popular in all
disciplines, including architecture and
engineering. Despite the fact that LCA
has been used for thousands of research
projects analyzing the environmental
characteristics of materials, components,
and even entire buildings, and is widely
described in books and scientifi c
publications, doubts and criticisms
still exist in the scientifi c community
about the eff ectiveness and accuracy
of LCA methods in accounting for all
environmental characteristics of buildings
and the built environment (Lenzen, et al.,
2004) (Zamagni, et al., 2008).
There are three main methodologies
found in literature for performing a LCA
(Treloar, 1998):
1. Process-based LCA: In a process-based
assessment, the process to be analyzed
is divided into all of its sub-processes.
The inputs and outputs of each
sub-process are quantifi ed and the
process analysis is repeated on all of
the inputs, tracing the processes back
to a “cradle,” where raw materials are
excavated or harvested. This method
has several problems, most notably
concerning the arbitrary process of
defi ning the boundaries of the analyzed
system (to decide which processes
are to be included or excluded from
the analysis) and the availability and
reliability of information regarding
upstream processes. It is also a very
time consuming and complex method.
On the other hand, the process-based
analysis is notable for its specifi city and
precision when it comes to detailed
product studies.
2. Input-output LCA: In input-output
assessment, all production inputs are
converted into economic factors using
industry-aggregated data on economic
interchanges. All of the infi nite material
and non-material upstream inputs
are included in the analysis using a
mathematic algorithm. This method has
been adapted from the environmental
analyses that emerged from the
research developed by Nobel Laureate
W. Leontief in the 1940s. The problem
with this method is that it uses industry-
wide average data, and therefore is
not specifi c to a single product, site, or
country, and the production processes
and technologies for the same product
can be very diff erent in diff erent parts
of the world. The positive aspect of this
method lies in its ability to assess the
seemingly infi nite upstream processes
with a quick, simple calculation method.
3. Hybrid LCA: Hybrid systems can either
be based on an input/output analysis
3.0 Life Cycle Assessment
| Life Cycle Assessment
Figure 3.1: Life Cycle Assessment Framework from ISO 14040:2006
Source: CTBUH
35
Life Cycle Assessment Framework
Goal
Defi nition
Scope
Defi nition
Inventory
Analysis
Interpretation
Impact
Assessment
data; and fi nally, the declaration of the
results‘ reproducibility.
• Inventory analysis: during this phase,
all inputs and outputs of the process
are acquired and described in line
with the goal and scope defi nitions. It
is usually the most time-consuming
phase of a LCA, as it requires
collecting and measuring a large
quantity of data, which often comes
from external sources. It is from the
accuracy and completeness of the LCI
that a LCA study gains its quality.
• Impact assessment: The Life Cycle
Impact Assessment (LCIA) is the phase
in which all inputs and outputs to
the process collected during the LCI
phase, are converted into impact
indicators. Impact indicators are the
tools that measure the impact of an
analyzed process on target categories
such as human health, the natural
environment, and natural resources.
• Interpretation of results: The
interpretation of results is often the
most interesting and “proactive” phase
of a LCA, as it gives recommendations
on how to improve a process or
selects the better process when two
processes are compared.
3.2 Defi nition of the Goal of the Study
The intended application of this study is
to inform the community of professionals
and researchers specializing in tall buildings
on the environmental performance of
the most common structural systems
(reinforced concrete, steel and composite
structural alternatives) by providing
the most accurate, up-to-date analysis
on two key impact categories: Global
Warming Potential (GWP) and Embodied
Energy (EE). The limitations of this study
are represented by the fact that only
two impact categories (GWP and EE)
are considered here, while other impact
categories may lead to diff erent results.
Similarly, the obtained results are infl uenced
by the quality of the information used,
both in terms of environmental data (i.e.,
the “quality” and representativeness of
the environmental data contained in the
international databases used in the study)
and data completeness (for example,
environmental data on the end-of-life of tall
buildings simply doesn’t exist, and had to
be collected specifi cally for this research).
The studied scenarios are representative of
the most common structural systems for
buildings of the height here considered.
This research is a complete Life Cycle
Assessment of structural systems for 60-
and 120-story buildings.
The main reason to conduct this study
is that there is a lack of reliable and
comprehensive information on the
environmental impacts of various
structural systems and materials for tall
buildings, as well as the impacts of the
construction phase on such projects. Also,
a comparison on the relative importance
of selecting various structural materials
and structural systems for a tall building
is needed. The intended audience of
this public study is the community
of tall building experts involved in the
Life Cycle Assessment |
Figure 4.1: Schematic of a Blast Oxygen Furnace
Source: Yellishetti et al, 2011, redrawn by CTBUH
STOCKHOUSE
IRON ORECOKE
LIMESTONEDOLOMITE
PARTICULATE EMISSION
GASCLEANING
BOILERS
COMBUSTIONAIR 80%
EFFICIENCY
CENTRAL BOILER STATION
COLD STEAMELSEWHERE
STEAM 3100 kPa400°C COKE OVEN
CONDENSERS
BLOWINGENGINE
1035 kPaSTEAM
AIRTURBINE
AIRTURBINE AIR
TURBINE(C, Fe)
Cast HouseEmissions
Control
FLUEDUSTFe, C, S
COLDBLAST
Raw BFGN2
CO2
NO2
BFG (exported)
COLD BLAST AIRHEAT OF COMPRESSION 150°C
HOT BLASTWIND
O2
IRO
N(F
e,
C, S
)
SLA
G (C
a, S
, F)
PART
ICU
LATE
(NO
2)
CO2,
SO2,
NO
X
EMIS
SIO
NS
CO2,
H2O
, NO
X
EMIS
SIO
NS
FEED
WA
TER
FUEL
STOVES1/3 BURN150°C
TO SINTER PLANT
ELECTRICITY
46
4.0 Steel: Cradle to Grave
Steel is a highly demanded product used
for many purposes, including buildings
and automobiles. The use of steel as a
structural element in buildings goes
back to the mid-18th century, when the
industrialized production of steel was
made possible. It is a metal product with
the unique ability to withstand both
compression and tension forces, making it
a great candidate for building structures.
As the construction of tall buildings
became a trend in the 20th century, steel
framed structures have become very
popular. Their light weight in comparison
to concrete or masonry structures,
their capability of holding large forces
(both horizontal and vertical) over wide
carbonated to make steel. The steel is then
molded and rolled into the desired shape
(Yellishetty, et al., 2011).
There are only a few integrated BOF
mills in the United States that are able
to produce large amounts of high-grade
steel, a material mainly used in big steel
profi les such as large structural steel
sections and sophisticated steel products
such as high-strength steel or alloy steel.
As steel is a highly recyclable material, a
signifi cant part of the new steel produced
in the industry, especially in Europe and
North America, is made out of recycled
steel scrap. This production method
utilizes Electric Arc Furnaces (EAF). Unlike
spans, and relatively small profi le (which
results in more space effi ciency) are the
qualities that gave rise to the popularity of
structural steel products.
4.1 Steel Production
Steel is produced using a complicated and
energy-intensive process: it is produced
through the carbonation of iron (pig iron
or cast iron made of iron ore). This initial
production procedure is done in blast
oxygen furnaces (Yellishetty, et al., 2011).
A Blast Oxygen Furnace (BOF) uses iron
ore, oxygen blast, and coke, heating the
compounds to make pig iron (see Figure
4.1). The produced iron pellets then get
| Steel: Cradle to Grave
Figure 4.2: Schematic of an Electric Arc Furnace
Source: Yellishetti et al, 2011, redrawn by CTBUH
47
et al., 2010), although the impact of steel
production in EAFs also vary based on
the energy source used to generate the
required electricity.
Although most new steel mills use
electricity as their power source instead
of burning coal or natural gas (ATHENA
Sustainable Materials Institute, 2002), the
average carbon footprint (1.77 kg CO2/
kg average) and embodied energy (24.4
MJ/kg average) of steel products is on par
with the average of the world’s combined
production processes (Hammond &
Jones, 2008).
There are two grades of steel used in the
tall building structures considered in this
research; normal-strength (50 Ksi/345 MPa)
and high-strength (65 Ksi/450 MPa).
Although normal-strength and high-
strength steel are not very diff erent in
terms of embodied energy and CO2
emissions (Stroetmann, 2011), the use
of high-strength steel in tall building
structures helps reduce the environmental
impacts of steel by using a smaller
quantity of steel profi les.
Although the high-strength steel used
in steel structures is mostly limited to
blast oxygen furnaces, EAFs use electrical
energy to melt steel scrap and form the
molten steel back into various shapes
though molding and rolling (Yellishetty,
et al., 2011) (see Figure 4.2). In 2014, 60%
of steel in the EU was produced with the
BOF method, while the remainder came
from EAFs. In the US, the above mentioned
percentages were inverted, with 40%
coming from BOFs, and 60% from EAFs
(WorldSteel, 2014).
Although the BOF method uses mostly
virgin iron and the EAF method uses
mostly scrap as the raw material, there is
still scrap used in the BOF steelmaking
process (about 25% scrap is used in BOF
furnaces) and some virgin iron is needed
in EAFs (5% virgin iron on average). The
steel made in combination mills, which
use a combination of EAFs and BOFs,
thus contain an average amount of steel
scrap based on the proportion of each
production route in the overall number
of steel products (Briggs, et al., 2010).
Production data for steel typically utilizes
an average of these routes, on both
national and international levels.
The steel products from EAF mills are
usually smaller in size and sometimes
lower in grade compared to the steel
from integrated BOF mills. Steel rebar
and other reinforcement steel products
are mostly produced using the EAF
method and thus contain signifi cant scrap
content, while structural steel sections
are produced using both EAF and BOF
routes (Yellishetty, et al., 2011). The actual
scrap ratio of various steel products may
diff er based on the location of their source
and, consequently, the environmental
impacts associated with steel production
can vary by production process. The
coke-making and iron-making processes
in a BOF mill contribute much more to
the environmental impacts of steel than
the electricity used in EAF mills (Briggs,
HOT IRONSCRAPDOLOMITEBURNT LIMEFLUORSPAR
LIQUIDSTEEL SLAG
EMISSION CONTROLparticulate
STEAM
ELECTRICITY
Fe
O295% CO
INFILTRATIONO2, N2
FLARED STACKCO2 EMISSIONS
GAS ANALYSISIN HOOD
(circa 80% CO)
C Fe
CFe
C
Fe
C
Fe
C Fe
CFe
C
Fe
C
Steel: Cradle to Grave |
Figure 5.1: Cement clinker
Source: (cc-by-sa) Amit Kenny
60
Various types of concrete are used in high-
rises: normal and lightweight (especially
for fl oor systems); and conventional and
high performance (with higher strength,
durability, and workability). These are often
integrated in the technologies adopted
in tall buildings, which can vary from
traditional Reinforced Concrete (RC) to
post-tensioned systems that use high-
performance concrete.
Although in some recent studies
(Weisenberger, 2010), where the benefi ts
of structural steel frames have been
demonstrated (reduced column sizes,
high strength-to-member-size benefi ts),
concrete systems have gained great
acceptance and the material has been
widely used by designers, especially
since the 1970s. This is partially related
to the fact that the concrete wall is the
stiff est element currently in the structural
engineer’s tool kit when conceiving
tower framing systems. Tall building
design is often controlled by stiff ness
more that strength. Also, concrete can
be poured into diff erent shapes, even
under extreme weather conditions and
temperatures, and is easily delivered
to job sites (concrete plants tend to be
conveniently located, even to city centers
and busy metropolitan areas). Aggressive
environmental conditions are countered
with additives that are able to signifi cantly
enhance the durability of the material.
As a consequence of the increase of
concrete use, the environmental impact
of concrete production is growing.
Concrete production is considered to be
responsible for up to 10% of global CO2
emissions (Ochsendorf, 2005), including
infrastructure construction.
5.1 Cement Production and
Transportation
Cement consists of a controlled chemical
combination of calcium oxides, silicon,
aluminum, iron, and other ingredients.
The most common manufacturing
process for cement is a dry method.
After quarrying raw materials including
limestone, shells, and chalk (or marl),
they are crushed in several stages using
crushers and hammer mills. Crushed rock
is then combined with other components
such as shale, clay, slate, blast furnace slag,
silica sand, and iron ore. The mixture is fed
into a cylindrical steel rotary kiln that heats
the ingredients to about 1480°C, powered
by burning powdered coal, oil, alternative
fuels, or gas under a forced draft. This
heating and mixing process releases both
clinker and gasses. Clinker (see Figure 5.1)
is brought down to handling temperature
in coolers. In order to increase burning
effi ciency and save fuel, heated air is
returned to the kilns. The cooled clinker is
then mixed with small amounts of gypsum
and limestone, then ground to a fi ne
powder commonly known as cement.
Among all concrete production
procedures, cement production is
responsible for the greatest amount of
CO2 emissions: on average, every ton
of cement produces 0.9 tons of CO2.
Although cement industries have focused
their eff orts on reducing CO2 emissions
related to the thermal energy of clinker
production, little can be done to reduce
the carbon released from limestone
decomposition, unless the amount of
Portland cement is minimized in the
design mix.
In fact, it is important to note in the
equation below, CO2 is not released just as
a consequence of the fossil fuels burnt to
heat the mixture in the kiln, but also as a
by-product of the chemical reaction that
transforms the limestone in clinker, with
the following percentages (Kestner, et al.,
2010): 40% from the production of clinker;
5.0 Concrete: Cradle to Grave
| Concrete: Cradle to Grave
61
60% from the decomposition of limestone
under high temperatures (above 1370°C).
Simplifi ed chemical reaction of cement
production:
CaCO3 + Heat → CaO + CO
2 ↑
Considering that 15% to 20% of cement
is used in conventional concrete mixes,
replacing 50% of cement with fl y
ash or other substitutes can lead to a
signifi cant reduction in CO2 related to
the “carbonation” of cement. A good
concrete mix design is one that meets
the required levels of workability,
strength, and durability for every building.
However, in order to meet more stringent
sustainability requirements, the designer
may consider using non-cement binders
and recycled aggregates.
The cement industry produces about
7% of global manmade CO2 emissions
(Ochsendorf, 2005), of which 60% arises
from the chemical process, and 40% from
burning fuel. Emissions from cement
production plants, apart from CO2, include
dust, nitrogen oxide (NOx), sulphur oxide
(SOx), as well as some micro-pollutants
(World Business Council for Sustainable
Development, 2002). Heavy metals (Tl, Cd,
Hg, etc.) are often found as trace elements
in common metal sulfi des. Pyrite (FeS2),
zinc blende (ZnS), and galena (PbS) are
present as secondary minerals in most of
the raw materials.
In terms of energy consumption, cement
production requires 4 GJ of energy per
ton of clinker produced (Kestner, et al.,
2010). Typical primary fuels used in clinker
production are fossil fuels such as coal
and petroleum cokes, as well as natural
gas and oil. It is possible to use selected
waste that meets strict specifi cations for
combustion in a kiln, partially replacing
fossil fuels. This waste often contains not
only recoverable calorifi c value, but also
useful minerals such as calcium silica,
alumina, and iron; therefore, it can be used
as raw material in the kiln. However, the
distinction between alternative fuels and
alternative raw materials is not always
clear, since some of them are characterized
by both recoverable calorifi c value and
useful minerals. Organic substances as
well as alternative fuels can be used for
this purpose, since the high temperatures
of the kiln gasses destroy the toughest
organic substances.
Sustainability is not an empirical property
of materials, since the choice of suitable
materials cannot be based on numerical
parameters, as is done in the process
of selecting materials for their strength
and elasticity characteristics. Therefore,
in assessing the sustainability of building
materials it is necessary to compare and
quantify the environmental impacts as
well as identify the context in which the
material will be applied.
Cement leaves the cement plant and
is transported to either a distribution
terminal or a fi nal customer, such as a
concrete production plant or a ready mix
plant. Transportation and distribution
occurs via boat, train, or truck. Cement
transportation requires special care in
order to avoid: contamination by residues
or previous cargoes; solidifi cation, if
cement is exposed to humidity and wet
conditions; and dust released during
loading (dust can react with water and
harden, damaging the transportation
tools). Transportation by ship is particularly
diffi cult: specialized ships called cement
carriers are available with diff erent
capacities. More advanced technologies
include cement carriers equipped with self
discharging systems.
As the commodity cost is quite low,
transportation cost is a key factor in
competitively supplying customers
with cement.
5.2 Cement Substitutes
The American Concrete Institute’s
Building Code Requirements for Structural
Concrete (ACI318-11) defi nes a High
Performance Concrete (HPC) as a special
engineered concrete in which one
or more specifi c characteristics have
been enhanced through the selection
of components. Thus, the concept of
HPC has been evolving since the 1970s.
For this reason Mehta (Mehta, 2004)
suggests that the term “high performance”
should be applied to the entire family
of concrete mixtures that off er higher
strength, higher durability, and higher
workability. One of the engineered
processes of HPC production is the partial
substitution of Portland cements in mix
“...Cement substitutes...reduce the carbon footprint, embodied
energy, material waste in landfi lls, extraction
of virgin materials and the environmental
impacts related to manufacturing Portland cement
clinker...”
Concrete: Cradle to Grave |
88
Building Name City Height Year of Demolition Reason for Demolition
One World Trade Center New York City (US) 417 m 2001 Uncontrolled collapse due to terroristic attack
Two World Trade Center New York City (US) 415 m 2001 Uncontrolled collapse due to terroristic attack
Singer Building New York City (US) 187 m 1968 Demolished to make room for 1 Liberty Plaza
Seven World Trade Center New York City (US) 174 m 2001 Uncontrolled collapse due to terroristic attack
Morrison Hotel Chicago (US) 160 m 1965 Demolished to make room for the First National Bank Building (now Chase Tower)
Deutsche Bank New York City (US) 158 m 2011 Irreparable damages caused by previous terroristic attack
One Meridian Plaza Philadelphia (US) 150 m 1999 Irreparable damages caused by fi re
Table 8.1: Recent Cases of Demolished Tall Buildings (italics denote buildings demolished through catastophic events)
Source: CTBUH
8.0 The End-of-Life of Tall Buildings
The CTBUH Skyscraper Center database
(Council on Tall Buildings and Urban
Habitat, 2015) shows that only seven
buildings taller than 150 meters have ever
been demolished to date (see Table 8.1).
However, this list includes the two tallest
buildings ever demolished, the World
Trade Center Twin Towers, which collapsed
as a consequence of the terrorist attacks of
September 11, 2001, together with Seven
World Trade Center that collapsed at the
same time. Excluding these three cases,
only four buildings taller than 150 meters
have ever been voluntarily demolished,
with the 187-meter Singer Building
(demolished in 1969) holding the title
of the tallest building ever dismantled,
followed by the 1965 demolition of the
Morrison Hotel in Chicago. Interestingly,
the Deutsche Bank building in New
York City and the One Meridian Plaza in
Philadelphia (respectively the 6th and 7th
tallest in the list) have been demolished,
though not as proper demolition
projects, but as a result of consequences
suff ered during two catastrophic events
(9/11 for the former, and a fi re occurring
in 1991 for the latter).
Except for a few demolitions that cleared
the way for the construction of bigger
towers during the 1970s, one could say
that signifi cant tall buildings are almost
never demolished. A number of options
exist to rejuvenate old towers (Trabucco &
Fava, 2013) and demolition is typically not
the preferred response to the evolution of
market needs, but more demolitions will
likely take place in the future as many tall
buildings are now approaching the end of
their service lives.
Fast growing economies are putting ever
increasing pressures on city centers, with
a continuous demand for new offi ces,
luxury hotels, and trophy residences.
While nobody argues that many iconic
buildings are likely to grace a city’s skyline
for centuries, evidence shows that typical
tall buildings suff er from a much faster
aging processes, not in terms of structural
and material obsolescence, but in terms of
functional obsolescence. One of the most
striking examples may be the 142-meter
Ritz-Carlton hotel in Hong Kong that
was demolished a mere 16 years after
construction to be replaced with a taller
offi ce tower as a consequence of Hong
Kong’s booming offi ce market.
8.1 High-Rise Demolition Techniques
Implosions are the most dramatic way
to demolish buildings and they have
been adopted in a number of cases (Liss,
2000), especially in the US. At 125-meters,
the Great Hudson Store in Detroit is the
tallest building ever imploded. Though
this system is still widely used, it is being
banned in most downtown areas due
to the heavy impact it has on the city in
terms of dust and pollution. Even where
it is allowed, assurance liabilities and
preparative mitigation works on nearby
buildings make this system unsuitable for
large-scale tall buildings in dense urban
environments. On February 2013, the
116-meter AfE Turm in Frankfurt, Germany
was imploded, making this the second-
tallest building ever demolished with
explosives, though it likely had a bigger
volume than the Great Hudson Store.
A slight variation of the implosion system
is the controlled collapse system, which
has been applied at its largest scale on
a 14-story residential block in Vitry-sur-
Seine, France. With this method, the load
bearing structural system of the building
is weakened in a convenient location
| The End-of-Life of Tall Buildings
Figure 8.1: Kajima Demolition Method applied at the Kajima HQ, Japan
Source: Kajima Corporation
Figure 8.2: Taisei Corporation’s Ecological Reproduction System (Tecorep) applied at the Grand Prince Hotel, Japan
Source: Taisei Corporation
89
Building Name Height
Duration of
Demolition
Works
Notes
Deutsche Bank, New York 158 m 48 months
Actual duration of 47 months,
demolition halted for 9 months
due to a fi re
One Meridian Plaza, Philadelphia 150 m 24 months -
Ritz-Carlton, Hong Kong 142 m 12 months Small fl oor plate
Hennessy Centre, Hong Kong 140 m 18 months -
Table 8.2: Duration of Demolition Projects
Source: CTBUH
through pull-cables or hydraulic rams until
the tower collapses on itself. The weight
of the falling structure above the collapse
point crushes the lower portion with an
eff ect similar to the use of explosives.
Though this system is less dangerous in
some ways, it creates the same problems
as explosives and is therefore unsuitable in
dense urban environments.
Deconstruction (or dismantling) is a less-
invasive demolition method that can be
applied to any kind of structure and is
the most widely adopted system for tall
buildings. Deconstructing tall buildings
is a long term task that sometimes
requires more time than was needed
for the construction of the tower (see
Table 8.2). Before demolition starts, the
building must be protected with scaff olds
to prevent falling debris. The scaff olding
system can be “traditionally” supported
from the ground (and attached to the
main structure) or suspended from the
roof of the building and jacked down as
deconstruction proceeds downward. The
latter option was extensively covered by
the media in two very recent cases: the
demolition of the 74-meter UAP Tower
in Lyon, France as well as the 140-meter
Grand Prince Hotel Akasaka and the
Otemachi Financial Center, both in Tokyo
(Kayashima, et al., 2012).
Deconstruction requires the use of small
excavators and other machines hoisted to
the roof of a building. Structural elements
are demolished through shears, torches,
saws, and crushers. The limiting factors of
this method is the load bearing capacity
of the fl oor system (that needs to be able
to carry heavy equipment and building
debris), and the actual fl oor plan that
may prevent the presence of multiple
machines. Debris must be lowered with
a crane and cannot usually be dropped
via gravity into empty elevator shafts as
this will cause vibrations, danger for the
The End-of-Life of Tall Buildings |
We now fi nd ourselves in an age where “green design” is at the forefront of many
tall building projects around the world, where it seems that every year brings
new technologies and innovations that are touted as the be-all and end-all
for a long-term sustainable future. But these solutions tend to only reduce the
environmental impacts of a building during its operation phases, with the stages
before and after this period often neglected. This is perhaps best illustrated by
the fact that the world is currently constructing tall buildings in excess of 1,000
meters in height yet we have never demolished a building of even 200 meters in
height through conventional means. Despite this reality, our cities continue to be
fi lled with myriad skyscrapers, most of which are not given full considerations for
their entire life cycle, or end-of-life.
Through the Life Cycle Assessment (LCA) methodology, we can gauge the
environmental consequences of human actions by analyzing the fl ow of
materials used in a building and trace the environmental impacts linked to each
stage of its life cycle. When information from each stage is combined, a holistic
picture of environmental impacts can be formed for a given product, one that
acknowledges the various actions that are required to bring a single entity into
existence through contemporary means.
This research identifi es and compares the life cycle implications for the structural
systems found in 60- and 120-story buildings. It is intended to inform the
international community of professionals and researchers specializing in tall
buildings on the life cycle environmental performance of the most common
structural systems by providing the most accurate, up-to-date analysis on two
key impact categories: Global Warming Potential (GWP) and Embodied Energy
(EE). In doing this it presents interesting research results, and also lays down a
methodology in this emerging fi eld for others to follow.
Research Funded by:
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